The present invention relates to voice/image processing techniques and more particularly to method and apparatus of retrieving compressed data.
In recent years, voice/moving image coding systems (MPEG1:ISO/IEC 11172, MPEG2:ISO/IEC 13818 and the like) have been standardized and the number of applications has increased in which compressed data is stored in, for example, a hard disk. In this type of application, a technique of retrieving the contents of the coded data plays an important role.
For example, in an application of a supervisory system, a voice/moving image from a supervisory camera is coded (compressed) and is transmitted to a location where a supervisor is present through a transmission path. On the receiving side, the transmitted voice/moving image coded data is decoded (expanded) and is delivered to a loudspeaker or a monitor as well as being recorded on a hard disk. When an object being supervised is desired to be analyzed in detail later, necessary data must be retrieved from a plurality of coded data pieces which have been recorded as above.
Generally, in a conventional technique applicable to this case, the contents of each moving image coded data piece is confirmed by utilizing the high-speed reproduction function of the retrieving system. The moving image coded data consists of coded data pieces of sequential pictures (or frames) and therefore, the high-speed reproduction is realized by jumping a plurality of pictures to perform thin-out reproduction.
On the other hand, in VOD (Video On Demand), for example, a great number of moving image coded data pieces are stored and when necessary moving image coded data is desired to be retrieved, it is usual to first determine the necessary data from its title name or a preset representative image. But more detailed contents is again confirmed by utilizing the aforementioned high-speed reproduction.